In recent years, in the water heater market, water heaters that heat water inside a watt storage vessel by causing water that has been heated by a heat pump to circulate in a coil configured by a coiled tube placed inside the water storage vessel have come into widespread use.
In these water heaters, it is necessary to maintain the clearances between mutually adjacent loops of the tube of the coil at a constant to stabilize heat exchange performance; for example, in the water heater disclosed in EP 1,983,287 A1, a coil support member is inserted into clearances between mutually adjacent loops of the tube of the coil, and a fixing member that fixes the coil support member is inserted into a clearance between the coil support member and the tube. The coil support member does not become disengaged from the clearances between the mutually adjacent loops of the tube as long as the fixing member does not come off, and the clearances between the mutually adjacent loops of the tube are stable.